The present invention relates to a swash plate type variable displacement compressor.
A swash plate type variable displacement compressor includes a swash plate in a housing. The swash plate has an insertion hole through which a rotary shaft is inserted and is driven to rotate by the rotary shaft. Pistons are connected to the swash plate. The housing has therein a control pressure chamber. The pressure in a control pressure chamber is changed in response to the pressure of refrigerant gas introduced into the control pressure chamber, with the result that the inclination angle of the swash plate with respect to the axis of the rotary shaft is changed and stroke length of the piston is changed, accordingly. As a result, the discharge displacement of the compressor is changed.
In a swash plate type variable displacement compressor, compression reaction force acts on the swash plate from the piston. It is noted that the swash plate has a point at which one of the pistons is positioned at a top dead center, or the top dead center point and a point at which one of the pistons is positioned at a bottom dead center, or the bottom dead center point. This compression reaction force may cause the swash plate in a direction that is different from the direction in which the swash plate is inclined in accordance with the displacement control of the compressor, about the line connecting the top dead center point and the bottom dead center point of the swash plate. In such a case that the swash plate is inclined in such different direction, the edge of the inner peripheral surface of an insertion hole of the swash plate, which is perpendicular to the axis of rotation of the rotary shaft and the line connecting the top dead center point and the bottom dead center point of the swash plate, are brought into contact with the rotary shaft. Therefore, there is fear that the swash plate may fail to change its inclination angle smoothly.
Japanese Patent Application Publication No. 2000-170651 discloses a swash plate type variable displacement compressor which is designed to prevent the edge of the inner peripheral surface of an insertion hole of a swash plate from being brought into contact with a rotary shaft when the swash plate is inclined in a direction that is different from the direction in which the swash plate is inclined in accordance with the displacement control of the compressor.
Referring to FIG. 11 showing the swash plate type variable displacement compressor disclosed by the above Publication, the swash plate designated by reference numeral 101 has an insertion hole 102 through which a rotary shaft 103 is inserted. The swash plate 101 has two contact pins 104A and 104B that are formed extending from the inner surface of the insertion hole 102 in the direction (or the arrow direction Z10 in FIG. 11) that is perpendicular to the axis L11 of rotation of the rotary shaft 103 and the line connecting the top dead center point and the bottom dead center point of the swash plate 101. The contact pins 104A and 104B are provided in the inner surface of the insertion hole 102 at positions adjacent to one end thereof as viewed in the axial direction of the rotary shaft 103. The swash plate 101 further has two contact pins 104C and 104D that are formed extending from the inner surface of the insertion hole 102 in the direction that is perpendicular to the axis L11 of rotation of the rotary shaft 103 and the line connecting the top dead center point and the bottom dead center point of the swash plate 101. The contact pins 104C and 104D are provided in the inner surface of the insertion hole 102 at positions adjacent to the other end thereof as viewed in the axial direction of the rotary shaft 103. The contact pins 104A, 104B, 104C, 104D are in constant contact with the rotary shaft 103.
When the compression reaction force P10 from the pistons acts on the swash plate 101, the swash plate 101 tends to be inclined about the line L12 connecting the top center point and the dead center point of the swash plate 101 in a direction that is different from the direction in which the swash plate 101 is inclined in accordance with the displacement control of the compressor (or arrow R10 in FIG. 11). Since the contact pins 104A, 104B, 104C, 104D are in constant contact with the rotary shaft 103, the contact between the rotary shaft 103 and each of the edges 102A and 1028 of the inner peripheral surface of the swash plate 101, which are located in the perpendicular direction to the axis L11 of the rotary shaft 103 and the line L12 connecting the top center dead point and the bottom dead center point of the swash plate 101, are prevented. As a result, the inclination angle of the swash plate 101 is changed smoothly.
In the swash plate type variable displacement compressor of the above-cited application, however, the contact pins 104A, 104B, 104C, 104D are kept in constant contact with the rotary shaft 103 when the swash plate 101 tends to be inclined in the direction against the displacement control of the compressor by the compression reaction force P10 exerted from pistons and acting on the swash plate 101. Therefore, the friction occurring between each of the contact pins 104A, 104B, 104C, 104D and the rotary shaft 103 prevents smooth change of the inclination angle of the swash plate 101.
It may be contemplated to set the spaced distance between the inner peripheral surface of the insertion hole 102 of the swash plate 101 and the rotary shaft 103 is larger enough for the edges 102A, 1028 not to be brought into contact with the rotary shaft 103 when the swash plate 101 is inclined in the direction against the displacement control of the compressor. In this case, however, the swash plate 101 tends to move easily toward the direction that is perpendicular to the axis L11 of the rotary shaft 103 and to the line L12 connecting the top center point and the dead center point of the swash plate 101, with the result that the positioning accuracy of the swash plate 101 with respect to the rotary shaft 103 deteriorates.
The present invention is directed to providing a swash plate type variable displacement compressor that permits smooth changing of the inclination angle of the swash plate while maintaining accuracy in the positioning of the swash plate.